A turbocharger is usually used for increasing the power of internal combustion engines by utilizing exhaust gas energy. For this purpose, the turbocharger is composed of a compressor and a turbine which are connected to one another via a shaft mounted within a bearing housing.
During operation, the turbine is set into rotation by an exhaust gas flow, and via the shaft drives the compressor, which draws in and compresses air. The compressed air is led into the engine, a large quantity of air entering into the cylinders during the induction stroke due to the increased pressure. As a result, the oxygen content required for the combustion of fuel correspondingly increases, so that more oxygen enters into the combustion chamber of the engine with each intake stroke.
This results in an increase in the maximum torque, causing the power output, i.e., the maximum power at a constant working volume, to increase. This increase allows in particular the use of a more powerful engine having approximately the same dimensions, or alternatively, allows a reduction in the engine dimensions, i.e., achieving comparable power with smaller and lighter machines.
During operation of a turbocharger, the shaft rotates at a high rotational speed with increasing engine speed. Due to the high rotational speed, vibrations which are caused, for example, by rotation of the shaft may be transmitted to the individual components of the bearing unit. In principle, a so-called quenching oil film which is formed in the space between the outer bearing ring and the bearing housing is used to damp these vibrations and thus prevent contact between the bearing components to be able to ensure proper operation of a turbocharger.
A bearing device for a turbocharger of the type mentioned at the outset is known from DE 35 31 313 C3. The bearing unit includes a bearing, designed as a ball bearing, which is accommodated in a bushing. The bushing, in turn, is positioned in a bearing housing. Recesses which together form a hole are introduced into the outer peripheral surface of the bushing and into the inner peripheral surface of the bearing housing. For positioning the bushing within the bearing housing, a securing element designed as a pin is provided which is loosely inserted into the recesses, i.e., the hole. The rotation of the outer bearing ring may be prevented in this way.